In the semiconductor industry, metrology plays a major role in the development of technology, as it allows providing the necessary information to characterize the features and properties of integrated devices. With the emergence of device concepts whereby dimensions are shrinking and/or functionality is increased, further requirements on the characterization techniques are imposed. One of these requirements is to derive the two-dimensional (2D) and/or three-dimensional (3D) dopant and/or free charge carrier distribution of a doped region in the integrated device. This distribution determines to a great extent the device performance, in particular when further down-scaling the device dimensions.
Thanks to its high spatial resolution, high sensitivity and high signal-to-noise ratio, scanning spreading resistance microscopy (SSRM) is implemented for mapping the free charge carrier distribution of a doped region. This technique is derived from the spreading resistance probe (SRP) technique, but it uses a much smaller tip mounted on an atomic force microscope (AFM) to probe the local spreading resistance of the doped region.
Despite the advantages offered, state-of-the-art SSRM is less able to provide accurate information on the spatial distribution of the free charge carriers of higher doped semiconductor devices, such as a FinFET or a Nanowire FET, in particular when the dimensions of the doped regions are further scaled down.